1. Field of the Invention
This invention, relates generally to a cyclone type gas-liquid separator for separating a liquid component contained in gas by a centrifugal force, which is, for example, used as an oil mist separator for separating oil mist contained in blow-by gas in a positive crankcase ventilation system.
2. Description of the Related Art
In a positive crankcase ventilation system, blow-by gas leaked into a crankcase through a gap between a piston and a cylinder wall is returned to an intake system, and accordingly is prevented from being emitted into atmosphere. The crankcase is connected to an intake pipe via a circulation flow passage equipped with a PCV valve, and forcibly discharges blow-by gas therein by utilizing a negative pressure in the intake pipe. Accordingly, unburned HC (hydrocarbon) contained in the blow-by gas is burned in an engine and the inside of the crankcase is ventilated, thereby preventing deterioration of engine oil.
Generally, blow-by gas contains a misty oil component (oil mist). To prevent oil mist from flowing into the intake pipe, conventionally, an oil mist separator is disposed in the circulating flow passage extending to the intake pipe. The oil mist separator conducts blow-by gas into a cylindrical cyclone chamber and makes it swirl flow, and the oil component contained in the blow-by gas is separated due to a centrifugation action thereof. The separated oil component is discharged through an oil discharge pipe to an oil pan or the like. The gas from which the oil component is separated is returned into the intake pipe through a gas outlet provided at an upper end portion of the cyclone chamber.
In this kind of cyclone type oil mist separator, it is required to improve an oil separation efficiency to decrease an amount of oil flowing into the intake pipe. In this connection, for example, JP-A-11-264312, discloses a structure in which swirl flow in a gas lead-through pipe extending upward from a gas outlet is enhanced by making a minimum cross-sectionial area of the gas lead-through pipe smaller than a cross-sectional area of a gas inlet communicating with a cyclone chamber, and an oil component that is to flow into the gas lead-through pipe is scattered in an oil spreader chamber at an upper side there of.
In this structure, because the centrifugation effect of the swirl flow is enhanced, separation and collection efficiencies of the oil component can be improved. However, because the cross-sectional area of the gas lead-through pipe is decreased, there arises a problem that a pressure loss in the device is increased.
The present invention has been made in view of the above problem, and an object of the present invention is to improve a separation, efficiency of gas and liquid without increasing a pressure loss in a cyclone type gas-liquid separator.
According to the present invention, a gas-liquid separator has a generally cylindrical vessel defining therein a cyclone chamber and having a gas inlet being open on an inner circumferential wall of the cyclone chamber for introducing a gas into the cyclone chamber. A gas lead-through pipe has a gas outlet and communicates with the cyclone chamber through the gas outlet. The gas outlet is disposed separately from the gas inlet in an axial direction of the vessel.
Further, a baffle plate is disposed in the cyclone chamber and generally dividing a space between the gas outlet and the gas inlet to form a gas flow flowing from the gas inlet toward the gas outlet along the inner circumferential wall. The gas lead-through pipe protrudes from the baffle plate at an opposite side of the gas inlet.
In the constitution described above, because the inside of the s chamber is divided by the baffle plate into a gas inlet side space and a gas outlet side space, gas introduced from the gas inlet is prevented from being drawn directly by a negative pressure of the gas lead-through pipe without swirling sufficiently, and the gas can form a swirl flow flowing along the inner circumferential wall. As a result, a separation efficiency of a liquid component from gas is improved. Because there is no need to decrease a cross-sectional area of the gas lead-through pipe and the swirl flow progresses smoothly along the inner circumferential wall, no disturbance of the flow occurs and pressure loss is lowered.
Because the lead through pipe protrudes from the baffle plate at the opposite side of the gas inlet, the liquid component separated from the gas is difficult to be discharged through the gas outlet. Further, the effect for making the gas flow along the inner circumferential wall is enhanced.
Preferably, the gas lead-through pipe penetrates a generally central portion of an en d wall of the cyclone chamber to extend in the cyclone chamber. Accordingly, the effect of the gas lead-through pipe to the swirl flow becomes small.
Preferably, the baffle plate is disposed along the inner circumferential wall at a position closer to the gas outlet than to the gas inlet. Accordingly, disturbing the swirl flow at the side close to the inner circumferential wall becomes more difficult, resulting in improvement of the gas-liquid separation efficiency.